1. Field of the Invention
The fields of art to which the claimed invention pertains are catalytic composites as well as the manufacture and use thereof. More specifically, the claimed invention relates use of a catalytic composite comprising a zeolitic crystalline aluminosilicate dispersed in a porous inorganic oxide carrier material having a constituent comprising one or more rare earth oxides.
2. Description of the Prior Art
There are a number of continuous cyclical processes employing fluidized solid techniques in which carbonaceous materials are deposited on the solids in the reaction zone and the solids are conveyed during the course of the cycle to another zone where carbon deposits are at least partially removed by combustion in an oxygen-containing medium. The solids from the latter zone are subsequently withdrawn and reintroduced in whole or in part to the reaction zone.
One of the more important processes of this nature is the fluid catalytic cracking (FCC) process in which heavy petroleum hydrocarbon feed stocks boiling in excess of about 400.degree. F. are converted to lower boiling hydrocarbons in the motor fuel boiling range by heating them in contact with an amorphous silica-alumina catalyst maintained in a fluidized state. While other composites comprising silica, e.g. silica-zirconia, silica-magnesia, etc., have been known to catalyze the cracking reaction, the silica-alumina composite has been by far the most widely accepted catalyst in the industry. More recently, improved catalysts having the capability of yielding greater proportions of high octane gasoline have been prepared by the inclusion of a finely divided zeolite, or cyrstalline aluminosilicate, either naturally occurring or synthetically prepared, within the amorphous silica-alumina matrix. Prior inventors have prepared, tested and compared hydrocarbon conversion catalysts comprising a finely divided crystalline aluminosilicate distributed in an amorphous silica matrix on the one hand, and in an amorphous silica-alumina matrix on the other hand. Examples of such catalysts are as described or claimed in U.S. Pat. Nos. 3,312,615; 3,392,110; 3,503,874; 3,592,778; 3,669,903; 3,696,023; 3,849,291; 3,926,778; 3,939,058; 4,001,106 and 4,100,219.
The FCC reaction produces, in addition to the desirable products, such as the high octane gasoline, a quantity of undesirable products such as the carbonaceous material or coke that deposits on the catalyst. The above mentioned zeolite containing catalysts enable minimization of these undesirable products while maximizing the conversion to the desirable products. Continuous efforts are being made, however, to improve the performance of even the zeolite containing catalysts.
There are many zeolite containing FCC catalysts described in the art other than those mentioned above which achieve improved performance by the addition of certain ingredients either to the catalyst itself or to the materials used in the manufacture of the catalyst at one or more of the manufacturing stages. For example, U.S. Pat. No. 3,471,410 discloses a method of reducing coke formation and improving the selectivity and efficiency of a fluid catalyst by incorporating zirconium in the silica-alumina gel which is a precursor of the catalyst. Likewise, U.S. Pat. No. 4,107,088 teaches addition of additives such as titania, zirconia, iron oxide and ceria (a rare earth) to the FCC catalyst precursors. U.S. Pat. No. 3,556,988, on the other hand, teaches the post catalyst formation ion exchange of the sodium contained in the zeolite constituent of the catalyst by treatment with an aqueous solution of a rare earth.
We have discovered a catalytic composite and a method for its manufacture which when used in a process for cracking a hydrocarbon charge stock enables improved conversion to desirable products with a reduction in coke production.